Fertilizer recommendation: correlation and calibration study of soil P test for yard long bean (Vigna unguilata L.) on Ultisols in Nanggung-Bogor (Jurnal)
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
Fertilizer Recommendation: Correlation and Calibration Study of Soil P Test
for Yard Long Bean (Vigna unguilata L.) on Ultisols in Nanggung-Bogor
Anas Dinurrohman Susila1*, Juang Gema Kartika1, Tisna Prasetyo1, and Manuel Celiz Palada2
1
Department of Agronomy and Horticulture, Faculty of Agriculture, Bogor Agricultural University,
Jl. Meranti Kampus IPB Darmaga 16680, Indonesia
2
Crop and Ecosystems Management Unit, AVRDC-World Vegetable Center,
P.O. BOX, Shanhua,Tainan 74199, Taiwan
Received 14 Mei 2010/Accepted 8 July 2010
ABSTRACT
Yard long bean (Vigna unguilata L.) 777 was grown in Ultisols, which typically have low pH and high P-!xation, to
determine the best correlation of soil extraction methods for soil P with yields, and to develop soil P response categories.
The research was conducted at SANREM base camp in Hambaro Village, Nanggung, Bogor, Indonesia from April to August
2008. Treatments were arranged in a Split Plot Design with three replications. The main plots were treatments with soil P
status of 0X, ¼X, ½X, ¾X and X, where is X = 1,590.5 kg SP-36 ha-1 (36% P2O5) applied once a month before planting. The
subplots were P application rate of 0, 75, 150, 225 and 300 kg P2O5 ha-1. Yard long beans were planted in double rows per
bed, 60 cm between rows and 25 cm within rows, 2 seeds per hole, with plot size of 1.5 m x 5 m. Coef!cient correlation (r)
of extraction reagents Olsen, Bray-1, HCl 25%, and Mechlich-1 were 0.772, 0.765, 0.755, and 0.732, respectively. Based on
Olsen soil testing methods, soil response categories of very low, low, medium, and high were (ppm P2O5) # 18.40, 18.40 < P
< 117.27, 117.27 < P < 267.04, and $ 267.04 extracted-P, respectively. Based on Bray-1 soil testing methods, soil response
categories for low, medium, and high were # 87.81, 87.81 < P < 233.78, and $ 233.78 extracted-P (ppm P2O5), respectively.
Fertilizer recommendation based on the Olsen soil test for low response category was 185.75 kg P2O5 ha-1, and for the medium
soil category was 175.97 kg P2O5 ha-1. The Bray-1 soil test for the low response category was 184.31 kg P2O5 ha-1, and for the
medium soil category was 161.39 kg P2O5 ha-1.
Keywords: calibration, fertilizer recommendation, phosphorus, yard long bean
INTRODUCTION
Soil testing using a single-nutrient soil analysis in
Indonesia has been developing since 1970. However,
due to limited research funds, soil testing has not been
programmed continuously and recommendation of location
speci!c fertilization based on soil family has also not yet
been established (Al-Jabri, 2007). Correlation studies for
soil P testing have been conducted for rice (Nursyamsi et
al., 1993) and corn (Kasno et al., 2001), however it has
not been conducted for horticultural crop especially for
vegetable crops.
The basic purpose of soil fertility evaluation is to
provide information on the nutrient status of the soil and
to predict the relative responses to the added nutrients. The
Crop Nutrient Requirement (CNR) value is the amount of
various nutrients needed to produce optimum, economical
yields from a fertilization standpoint. It is important to
remember that these nutrient amounts are supplied to the
crop from both soil and fertilizer application. Phosphorus
(P) fertilizer will only be applied when a properly calibrated
* Corresponding author. e-mail: anasdsusila@yahoo.com
Fertilizer Recommendation: Correlation and Calibration......
soil test indicates very small extractable amounts of this
nutrient in the soil.
The nutrient status of cultivated soils varies and
is continually changing due to the in"uence of fertilizer
addition, nutrient losses by leaching or removal, and
overall management. Site-speci!c estimation of the nutrient
fertility status of soil are, therefore, very important for
rational fertilizer use. Reliable site-speci!c information can
only be accomplished through an orderly program of soil
fertility evaluation in which proper attention is given to the
following: 1) Techniques of soil sampling; 2) methods of
soil analysis; 3) systems for correlating soil analysis results
and crop responses; 4) model for interpretation of fertilizer
response in !eld trials, and 5) procedure for preparing
economically sound fertilizer recommendation.
Phosphorus is an essential component for many
physiological processes related to proper energy utilization
in plants. Phosphorus is used in several energy transfer
compounds in the plants. A very important function of P
is as an important element of nucleic acids, the building
blocks for the genetic code material in plant cells. Plants
derive their P needs from soil, and uptake P mostly in
the orthophosphate form. Native soil P levels are often
low enough to limit crop production. Both inorganic P
225
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
fertilizers (treated rock phosphate) and organic P sources
(animal manures) are equally adequate at supplying the
orthophosphate ion and correcting P de!ciencies in soil
(Daniels et al., 2008; Hochmuth, 2008).
Phosphorus fertilization is a key component in
increasing soil productivity and in maximizing yield of
crops. However, inputs of fertilizer and manure in excess of
crop requirements might lead to a build-up of soil P levels
and increased P runoff from agricultural soils. Phosphorus
loss in runoff from agricultural !elds has been identi!ed as
an important contributor to eutrophication (Dobermann et
al., 2002; Daverede et al., 2003).
Soil P tests are fundamental analytical tools for
assessing the P nutrient status of the soil. Normally, the
plants can utilize only a small percentage of the total soil P,
such a quantity being strictly correlated to the labile soil P
(portion of P relatively loosely bound to the soil colloids).
Soil test P is not an indication of total P in the soil but of
how much is available for plant use. Soil testing is the key
component for determining the need for P fertilization. Also,
if fertilization is required, soil test results guide the rate of
application recommended to optimize production (Sawyer
and Mallarino, 1999; Dobermann et al., 2002; Daniels et
al., 2008).
Soil extracting reagents like Mechlich-1, Olsen,
Bray-1, Morgan Vanema, HCl 25%, Water, Truog, and
other extracting reagent have been used in correlation and
calibration study of soil analysis and crop response of P in
many research project. This is an important consideration
as there have been many methods developed to test soils
for crop available P. Each can have a widely different
interpretation index (Sawyer and Mallarino, 1999). Kidder
et al. (2003) used Mechlich-1 to interprete P requirement for
environmental horticulture, and divided soil P status into 5
levels: very low (P < 10 ppm), low (P 10-15 ppm), medium
(P 16-30 ppm), high (P 31-60 ppm) and very high (P > 60
ppm).
Kelling et al. (1998) described several factor affecting
P recommendations, i.e. crop demand level (each crops
requires varying level of available P to optimize yield),
subsoil fertility (based on the subsoil nutrient supplying
power of the soil), the yield potential of the soil and the
farmers yield goals. Chang et al. (2004) reported that the
best approaches for minimizing recommendation errors
were nutrient speci!c. Phosphorus recommendations
were improved using multiple years of yield monitor
data to develop landscape-speci!c yield goals, sampling
old homesteads separately from the rest of the !eld, and
P recommendations. The objective of this study was to
build environmentally friendly fertilizer recommendations
based on soil analysis for vegetable production in Ultisols.
Speci!c objectives of this study were to !nd out the best soil
P extraction methods and response categories of soil-P on
yield of yard long bean.
226
MATERIALS AND METHODS
The research was conducted at SANREM base camp in
Hambaro Village, Nanggung, Bogor, Indonesia from April
to August 2008. The soils at the location are Ultisols, which
typically have low pH and high P-!xation by aluminum.
Treatments were arranged in a Split Plot Design with three
replications. The main plot treatment was soil P status and
the subplot was P rate. Soil P status was developed by
application of P at the rates of 0, 45, 90, 135 and 180 kg
P2O5 ha-1 from December 2006 to April 2007 for vegetables
production, followed by application of 0X, ¼X, ½X, ¾X
and X, where X = 1,590.5 kg SP-36 ha-1 (36% P2O5) one
month before planting. The subplot treatments were P rates
of 0, 75, 150, 225 and 300 kg P2O5 ha-1 applied as pre-plant
applications. Yard long beans, variety 777, were sown in
double rows per bed, 60 cm between rows and 25 cm within
rows, 2 seed per hole. The total plot number was 25 times 3
replications which is equal to 75 plots with individual plot
size of 1.5 m x 5 m.
Lime (CaCO3) was well incorporated (1 ton ha-1)
into the beds two weeks before planting. Furrow irrigation
was carried out at one-week intervals and weeding was
performed when necessary. Fertilizer rates for N and K were
135 kg K2O ha-1 and 100 kg N ha-1, respectively. Phosphorus
rates were applied based on treatment. Fifty percent of N
and K were applied pre-plant and the remaining applied
in two side dressings of 25 % each at 3 and 6 weeks after
transplanting. First pod harvesting was carried out at seven
weeks after planting, every 3-4 days. Soil samples for the
correlation test were taken two days before planting or 4
weeks after P status treatments were applied. Phosphorus
soil extracting reagents that had been evaluated were Bray1 (HCl 0.025 N + NH4F 0.03 N), Truog [H2SO4 0.002 N +
(NH4)2SO4; pH 3], Olsen (NaHCO3 0.50 N; pH 8.5), HCl
25%, Water, Mechlich-1 (HCl 0.05 N and H2SO4 0.025 N),
Morgan Vanema (NH4-OAc 1 M; pH 4.8) .
Measurement on plant height and plant diameter
were conducted at 2, 3 and 4 weeks after transplanting. Pod
weight per plot and marketable yield per plot were measured
at 7 weeks after transplanting. Analysis of variance of
data was calculated using SAS 8.12 (SAS Institute, N.C).
A correlation test was used to !nd out the best soil P
extracting reagent for yard long bean in acid soil (Ultisols).
Determination of soil P-response categories was conducted
based on the best crop response to soil P-extracting reagents.
The soil P response was divided into four categories; very
low if relative yield (RY) < 50%, low RY 50-75%, medium
RY 75-100%, and high RY = 100%. The critical border
to determine P soil index for each group is shown in the
calibration curve correlating P soil index (X) and relative
yield (Y). An orthogonal polynomial test was used to !nd
out the optimum fertilizer rate of P for maximum yield for
each soil response category.
Anas Dinurrohman Susila, Juang Gema Kartika, Tisna Prasetyo, and Manuel Celiz Palada
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
RESULTS AND DISCUSSION
Plant Growth and Yield
The effect of soil P status on plant height and stem
diameter was not signi!cant except on plant height at 2
weeks after planting. Application of P fertilizer to build
up soil P status from 0 to X = 1,590.5 kg SP-36 ha-1 (36%
P2O5) increased linearly for plant height from 2 weeks after
planting (Table 1). The same response was obtained on
marketable yield per plot (Table 2). Soil P status from 0
to 1,591 g SP-36 ha-1 increased marketable yield per plot
linearly from 2,167.4 to 2,920.6 g plot-1. However, there
was no signi!cant effect on non-marketable yield per plot
and pod length. These results indicated that the range of
soil P status in the research site was wide enough to build
a correlation study between soil P status and yield response
of yard long bean.
Correlation between Soil Extracted-P and Yield
Five different soil-P extraction methods resulted in
different soil-P indices. The strongest extracting reagents to
the weakest were HCl 25% (521–1,565 ppm P2O5) followed
by Mechlich-1 (30–841 ppm P2O5), Truog (13-489 ppm
P2O5), Olsen (43–417 ppm P2O5), Bray-1 (23-414 ppm
P2O5), Morgan Vanema (1–18 ppm P2O5), and water (0.1–1.6
ppm P2O5). Extracted-P by different extraction methods on
different P-application rates on Ultisols is presented in Table
3. The strongest extraction methods was not necessarily be
the best solution for soil P extraction. The ideal soil test
has the following characteristics: 1) the extracting reagent
is effective for most, if not all plant mineral nutrients, and
for all soil types, 2) the procedure accurately measures the
plant-availability of the nutrient, and 3) the test is simple,
inexpensive, quick, reproducible, and sensitive to all soil
factors controlling nutrient availability (Skogley, 1994).
In order for a soil test to be useful, there must be a
positive correlation between the index and the crop response
(yield). The best extraction method will mimic how the
plant root extracts P from the soil, therefore it will have
good correlation with plant yield. The highest coef!cient
correlation to the lowest was Olsen (0.772), Bray-1 (0.765),
HCl 25% (0.755), Mechlich-1 (0.732), Morgan Vanema
(0.650), Water (0.623), and Truog (0.266) (Table 4). For an
extracting reagent to be effective, it requires that a low index
Table 1. The effect of soil P status on plant height and stem diameter of yard long bean at 2, 3, and 4 weeks after planting
Soil P status by application
of SP-36 (kg ha-1)
0
(0X)
398 (1/4X)
795 (1/2X)
1193 (3/4X)
1591 (X)
Response
2
17.54b
18.88a
18.58a
19.28a
19.53a
L**
Plant height
(weeks after planting)
3
cm
42.67
51.54
48.64
49.01
53.47
NS
4
2
123.68
140.57
135.13
135.91
139.88
NS
0.317
0.364
0.387
0.349
0.411
NS
Stem diameter
(weeks after planting)
3
cm
0.413
0.440
0.449
0.459
0.467
NS
4
0.485
0.498
0.505
0.534
0.524
NS
Note: * = Signi!cant at 5% F test; ** = signi!cant on 1% F test; NS = Not Signi!cant; L = Linear
Table 2. The effect of soil P status on marketable yield, non-marketable yield and pod length of yard long bean
Soil P status by application of SP-36
(kg ha-1)
Marketable yield per plot
0
(0X)
398 (1/4X)
795 (1/2X)
1193 (3/4X)
1591 (X)
Response
g
2167.4 b
2614.2 ab
2816.4 ab
3058.0 a
2920.6 ab
L*
Non-marketable yield
per plot
g
372.68
474.40
435.18
515.61
485.91
NS
Pod length
cm
56.09
57.75
58.33
57.73
58.82
NS
Note: * = Signi!cant on 5% F test; NS = Not Signi!cant; L = Linear
Fertilizer Recommendation: Correlation and Calibration......
227
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
be related to reduced growth responses for a crop grown on
that soil, and conversely, a high index be related to maximum
crops response (Dahnke and Olson, 1990). Soil-P extraction
methods with coef!cient correlation > 0.7 (Olsen, Bray-1,
HCL 25%, Mechlich-1) can be recommended to test soil P
for yard long bean in Ultisols Nanggung, Bogor. However,
evaluation of the operational cost and reproducibility of that
extraction reagent is still needed.
Calibration of the Soil P Test
Once a good correlation between indices produced by
the extracting reagent and crop response is established, soil
test indices are usually grouped into response categories so
that the indices can be interpreted and become meaningful.
By plotting of percent relative yields and corresponding
extracted-P, it can be determined plant response categories
of that soil. Yard long bean relative yield plotted against
extracted-P by Olsen reagent is presented in Figure 1.
Extracted-P concentration # 18.40 ppm resulted in # 50%
crop relative yield and therefore was termed “very low”. A
“low” response category result of 50% to 75% of relative
yield was obtained where soil extracted-P was > 18.40 to <
117.27 ppm. A “medium” response category result of 75%
to 100% of relative yield was obtained where soil extractedP was > 117.27 to < 267.04 ppm, while a “high” response
category result of $ 100% of relative yield was obtained for
soil extracted-P $ 267.04 ppm.
Table 3. Extracted-P by various extraction methods from different P fertilizer rates on Ultisols, Nanggung, Bogor
Soil P status by
application of
SP-36 (kg ha-1)
0 (0X)
397,625 (1/4X)
795,250 (1/2X)
1,192,875 (3/4X)
Truog
54 ± 35.55
58 ± 54.22
77 ± 61.29
314 ± 151.84
Mechlich-1
HCl 25%
Olsen
Bray 1
(P2O5 ppm)
Water
Morgan
Vanema
------------------------- Extracted-P ----------------------51 ± 27.59
613 ± 114.18
62 ± 17.35
34 ± 1290
0.2 ± 0.10
2 ± 0.00
94 ± 29.57
704 ± 129.00 118 ± 100
60 ± 16.65 0.13 ± 0.06 2.3 ± 1.53
182 ± 91.76
742 ± 165.77 126 ± 43.41 108 ± 60.78 0.33 ± 0.23 5.3 ± 3.06
487 ± 309.02 1317 ± 303.04 324 ± 95.04 263 ± 132.22 0.37 ± 0.15 10.7 ± 6.66
Table 4. Correlation between extracted-P by different extraction reagents with yard long bean relative yield on Ultisols,
Nanggung, Bogor
Extraction reagent
Truog
Mechlich-1
HCl 25%
Olsen
Bray-1
Water
Morgan Vanema
Linear equation
RY= 70.563 + 0.064 P
RY= 66.673 + 0.052 P
RY= 47.280 + 0.034 P
RY= 61.548 + 0.097 P
RY= 64.248 + 0.108 P
RY= 67.724 + 32.239 P
RY= 66.465 + 2.239 P
Figure 1. Plot of relative yield and corresponding extracted-P using
Olsen extraction method in Ultisols, Nanggung, Bogor.
VL = Very Low, L = Low, M = Medium, H = High
228
Coef!cient correlation
0.566
0.732
0.755
0.772
0.765
0.623
0.650
Figure 2. Plot of relative yield and corresponding extracted-P using
Bray-1 extraction method in Ultisols, Nanggung, Bogor.
VL = Very Low, L = Low, M = Medium, H = High
Anas Dinurrohman Susila, Juang Gema Kartika, Tisna Prasetyo, and Manuel Celiz Palada
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
Plots of extracted-P by Bray-1 reagent with yard long
bean relative yield can be seen in Figure 2. There was no
“very low” response category obtained by Bray-1 soil P test
from this study. A “low” response category result (# 75%
of relative yield) was obtained with soil extracted-P # 87.81
ppm, a “medium” response category result (75 % to 100 %
relative yield) was obtained with soil extracted-P between
< 87.81 to < 233.78 ppm, while a “high” response category
result of $ 100% of relative yield was obtained with soil
extracted-P $ 233.78 ppm. The Olsen and Bray-1 soil test
calibration for yard long bean in Ultisols, Nanggung, Bogor
can be seen in Table 5.
Fertilizer Recommendation
The objectives of grouping soil test indices into
responses categories are to recommend the quantity of
fertilizer required for those sites to produce maximum yield.
The relationship between P-fertilizer rate and relative yield
of yard long bean on Ultisols, Nanggung, Bogor, based
on response category determined by different extraction
methods, can be seen in Figure 3. Based on Olsen extraction
methods, under “low” soil response category the regression
equation was RY = -0.00065x2 + 0.24147x + 62.89249, R2
= 0.26677. From this regression model, optimum predicted
P-fertilizer rate was 185.75 kg P2O5 ha-1 or equal to 515.96
kg SP-36 ha-1 (36% P2O5). Under “medium” soil response
category the regression equation was RY = -0.00068x2 +
0.23796x + 52.22694, R2 = 0.41078. Optimum predicted Pfertilizer rate for “medium” soil P response category was
174.97 kg P2O5 ha-1 or equal to 486.03 kg SP-36 ha-1 (36%
P2O5). Predicted P-fertilizer recommendation rate based on
soil-P response category can be seen in Table 6.
Based on Bray-1 extraction method, under “low”
soil response category the regression equation was RY =
-0.00059x2 + 0.21749x + 63.92204, R2 = 0.23603. From
this regression model, optimum predicted P-fertilizer rate
was 184.31 kg P2O5 ha-1 or equal to 511.98 kg SP-36 ha-1
(36% P2O5). Under “medium” soil response category the
regression equation was RY = -0.00099x2 + 0.31956x +
53.69884, R2 = 0.50473. Optimum predicted P-fertilizer
rate for “medium” soil P response category was 161.39 kg
P2O5 ha-1 or equal to 448.32 kg SP-36 ha-1 (36% P2O5).
Although there were differences in soil P category values
between Olsen and Bray-1 extraction methods, the predicted
P fertilizer recommendation were similar for the same soil P
category responses.
Figure 3. Relationship between P-fertilizer rate and relative yield of yard long bean on Ultisols, Nanggung, Bogor based on response
category determined by different extraction methods (A) Low soil-P response category by Olsen (B) Medium soil-P response
category by Olsen (C) Low soil-P response category by Bray-1 (D) Medium soil-P response category by Bray-1
Fertilizer Recommendation: Correlation and Calibration......
229
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
Table 5. The Olsen and Bray-1 soil test calibration for yard long bean in Ultisols, Nanggung, Bogor
Response category
Extracted-P (ppm P2O5)
Relative yield (%)
Very low
Low
Medium
High
Olsen
# 18.40
> 18.40 - < 117.27
> 117.27 - < 267.04
$ 267.04
# 50
> 50 - < 75
> 75 - < 100
$ 100
Bray I
# 87.81
< 87.81 - < 233.78
$ 233.78
Table 6. Predicted P-fertilizer recommendation rate for yard long bean in Ultisols, Nanggung , Bogor, based on soil-P
response category
Soil-P response
category
Olsen
Low
Medium
Bray-1
Low
Medium
Predicted P-rate (kg ha-1)
P2O5
SP-36
R2
185.75
174.97
515.96
486.03
RY = -0.00065x2 + 0.24147x + 62.892
RY = -0.00068x2 + 0.23796x + 52.227
0.26677
0.41078
184.31
161.39
511.98
448.32
RY = -0.00059x2 + 0.21749x + 63.922
RY = -0.00099x2 + 0.31956x + 53.699
0.23603
0.50473
CONCLUSION
From this study it can be concluded that Olsen, Bray-1,
HCl 25%, and Mechlich-1 soil test can be used to determine
soil-P for yard long bean production in Ultisols-Nanggung.
The coef!cient correlation (r) of extraction reagent Olsen,
Bray-1, HCl 25%, and Mechlich-1 were 0.772, 0.765, 0.755,
and 0.732, respectively. With the Olsen soil test, UltisolsNanggung can be divided into very low, low, medium and
high soil response category. However with the Bray-1 soil
test they only can be divided into low, medium, and high
soil response categories.
ACKNOWLEDGEMENT
This publication was made possible through support
provided by the United States Agency for International
Development and the generous support of the American
People (USAID) for the Sustainable Agriculture and Natural
Resources Management Collaborative Research Support
Program (SANREM CRSP) under terms of Cooperative
Agreement Award No. EPP-A-00-04-00013-00 to the Of!ce
of International Research and Development (OIRED) at
Virginia Polytechnic Institute and State University (Virginia
Tech).
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Madison.
231
Fertilizer Recommendation: Correlation and Calibration Study of Soil P Test
for Yard Long Bean (Vigna unguilata L.) on Ultisols in Nanggung-Bogor
Anas Dinurrohman Susila1*, Juang Gema Kartika1, Tisna Prasetyo1, and Manuel Celiz Palada2
1
Department of Agronomy and Horticulture, Faculty of Agriculture, Bogor Agricultural University,
Jl. Meranti Kampus IPB Darmaga 16680, Indonesia
2
Crop and Ecosystems Management Unit, AVRDC-World Vegetable Center,
P.O. BOX, Shanhua,Tainan 74199, Taiwan
Received 14 Mei 2010/Accepted 8 July 2010
ABSTRACT
Yard long bean (Vigna unguilata L.) 777 was grown in Ultisols, which typically have low pH and high P-!xation, to
determine the best correlation of soil extraction methods for soil P with yields, and to develop soil P response categories.
The research was conducted at SANREM base camp in Hambaro Village, Nanggung, Bogor, Indonesia from April to August
2008. Treatments were arranged in a Split Plot Design with three replications. The main plots were treatments with soil P
status of 0X, ¼X, ½X, ¾X and X, where is X = 1,590.5 kg SP-36 ha-1 (36% P2O5) applied once a month before planting. The
subplots were P application rate of 0, 75, 150, 225 and 300 kg P2O5 ha-1. Yard long beans were planted in double rows per
bed, 60 cm between rows and 25 cm within rows, 2 seeds per hole, with plot size of 1.5 m x 5 m. Coef!cient correlation (r)
of extraction reagents Olsen, Bray-1, HCl 25%, and Mechlich-1 were 0.772, 0.765, 0.755, and 0.732, respectively. Based on
Olsen soil testing methods, soil response categories of very low, low, medium, and high were (ppm P2O5) # 18.40, 18.40 < P
< 117.27, 117.27 < P < 267.04, and $ 267.04 extracted-P, respectively. Based on Bray-1 soil testing methods, soil response
categories for low, medium, and high were # 87.81, 87.81 < P < 233.78, and $ 233.78 extracted-P (ppm P2O5), respectively.
Fertilizer recommendation based on the Olsen soil test for low response category was 185.75 kg P2O5 ha-1, and for the medium
soil category was 175.97 kg P2O5 ha-1. The Bray-1 soil test for the low response category was 184.31 kg P2O5 ha-1, and for the
medium soil category was 161.39 kg P2O5 ha-1.
Keywords: calibration, fertilizer recommendation, phosphorus, yard long bean
INTRODUCTION
Soil testing using a single-nutrient soil analysis in
Indonesia has been developing since 1970. However,
due to limited research funds, soil testing has not been
programmed continuously and recommendation of location
speci!c fertilization based on soil family has also not yet
been established (Al-Jabri, 2007). Correlation studies for
soil P testing have been conducted for rice (Nursyamsi et
al., 1993) and corn (Kasno et al., 2001), however it has
not been conducted for horticultural crop especially for
vegetable crops.
The basic purpose of soil fertility evaluation is to
provide information on the nutrient status of the soil and
to predict the relative responses to the added nutrients. The
Crop Nutrient Requirement (CNR) value is the amount of
various nutrients needed to produce optimum, economical
yields from a fertilization standpoint. It is important to
remember that these nutrient amounts are supplied to the
crop from both soil and fertilizer application. Phosphorus
(P) fertilizer will only be applied when a properly calibrated
* Corresponding author. e-mail: anasdsusila@yahoo.com
Fertilizer Recommendation: Correlation and Calibration......
soil test indicates very small extractable amounts of this
nutrient in the soil.
The nutrient status of cultivated soils varies and
is continually changing due to the in"uence of fertilizer
addition, nutrient losses by leaching or removal, and
overall management. Site-speci!c estimation of the nutrient
fertility status of soil are, therefore, very important for
rational fertilizer use. Reliable site-speci!c information can
only be accomplished through an orderly program of soil
fertility evaluation in which proper attention is given to the
following: 1) Techniques of soil sampling; 2) methods of
soil analysis; 3) systems for correlating soil analysis results
and crop responses; 4) model for interpretation of fertilizer
response in !eld trials, and 5) procedure for preparing
economically sound fertilizer recommendation.
Phosphorus is an essential component for many
physiological processes related to proper energy utilization
in plants. Phosphorus is used in several energy transfer
compounds in the plants. A very important function of P
is as an important element of nucleic acids, the building
blocks for the genetic code material in plant cells. Plants
derive their P needs from soil, and uptake P mostly in
the orthophosphate form. Native soil P levels are often
low enough to limit crop production. Both inorganic P
225
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
fertilizers (treated rock phosphate) and organic P sources
(animal manures) are equally adequate at supplying the
orthophosphate ion and correcting P de!ciencies in soil
(Daniels et al., 2008; Hochmuth, 2008).
Phosphorus fertilization is a key component in
increasing soil productivity and in maximizing yield of
crops. However, inputs of fertilizer and manure in excess of
crop requirements might lead to a build-up of soil P levels
and increased P runoff from agricultural soils. Phosphorus
loss in runoff from agricultural !elds has been identi!ed as
an important contributor to eutrophication (Dobermann et
al., 2002; Daverede et al., 2003).
Soil P tests are fundamental analytical tools for
assessing the P nutrient status of the soil. Normally, the
plants can utilize only a small percentage of the total soil P,
such a quantity being strictly correlated to the labile soil P
(portion of P relatively loosely bound to the soil colloids).
Soil test P is not an indication of total P in the soil but of
how much is available for plant use. Soil testing is the key
component for determining the need for P fertilization. Also,
if fertilization is required, soil test results guide the rate of
application recommended to optimize production (Sawyer
and Mallarino, 1999; Dobermann et al., 2002; Daniels et
al., 2008).
Soil extracting reagents like Mechlich-1, Olsen,
Bray-1, Morgan Vanema, HCl 25%, Water, Truog, and
other extracting reagent have been used in correlation and
calibration study of soil analysis and crop response of P in
many research project. This is an important consideration
as there have been many methods developed to test soils
for crop available P. Each can have a widely different
interpretation index (Sawyer and Mallarino, 1999). Kidder
et al. (2003) used Mechlich-1 to interprete P requirement for
environmental horticulture, and divided soil P status into 5
levels: very low (P < 10 ppm), low (P 10-15 ppm), medium
(P 16-30 ppm), high (P 31-60 ppm) and very high (P > 60
ppm).
Kelling et al. (1998) described several factor affecting
P recommendations, i.e. crop demand level (each crops
requires varying level of available P to optimize yield),
subsoil fertility (based on the subsoil nutrient supplying
power of the soil), the yield potential of the soil and the
farmers yield goals. Chang et al. (2004) reported that the
best approaches for minimizing recommendation errors
were nutrient speci!c. Phosphorus recommendations
were improved using multiple years of yield monitor
data to develop landscape-speci!c yield goals, sampling
old homesteads separately from the rest of the !eld, and
P recommendations. The objective of this study was to
build environmentally friendly fertilizer recommendations
based on soil analysis for vegetable production in Ultisols.
Speci!c objectives of this study were to !nd out the best soil
P extraction methods and response categories of soil-P on
yield of yard long bean.
226
MATERIALS AND METHODS
The research was conducted at SANREM base camp in
Hambaro Village, Nanggung, Bogor, Indonesia from April
to August 2008. The soils at the location are Ultisols, which
typically have low pH and high P-!xation by aluminum.
Treatments were arranged in a Split Plot Design with three
replications. The main plot treatment was soil P status and
the subplot was P rate. Soil P status was developed by
application of P at the rates of 0, 45, 90, 135 and 180 kg
P2O5 ha-1 from December 2006 to April 2007 for vegetables
production, followed by application of 0X, ¼X, ½X, ¾X
and X, where X = 1,590.5 kg SP-36 ha-1 (36% P2O5) one
month before planting. The subplot treatments were P rates
of 0, 75, 150, 225 and 300 kg P2O5 ha-1 applied as pre-plant
applications. Yard long beans, variety 777, were sown in
double rows per bed, 60 cm between rows and 25 cm within
rows, 2 seed per hole. The total plot number was 25 times 3
replications which is equal to 75 plots with individual plot
size of 1.5 m x 5 m.
Lime (CaCO3) was well incorporated (1 ton ha-1)
into the beds two weeks before planting. Furrow irrigation
was carried out at one-week intervals and weeding was
performed when necessary. Fertilizer rates for N and K were
135 kg K2O ha-1 and 100 kg N ha-1, respectively. Phosphorus
rates were applied based on treatment. Fifty percent of N
and K were applied pre-plant and the remaining applied
in two side dressings of 25 % each at 3 and 6 weeks after
transplanting. First pod harvesting was carried out at seven
weeks after planting, every 3-4 days. Soil samples for the
correlation test were taken two days before planting or 4
weeks after P status treatments were applied. Phosphorus
soil extracting reagents that had been evaluated were Bray1 (HCl 0.025 N + NH4F 0.03 N), Truog [H2SO4 0.002 N +
(NH4)2SO4; pH 3], Olsen (NaHCO3 0.50 N; pH 8.5), HCl
25%, Water, Mechlich-1 (HCl 0.05 N and H2SO4 0.025 N),
Morgan Vanema (NH4-OAc 1 M; pH 4.8) .
Measurement on plant height and plant diameter
were conducted at 2, 3 and 4 weeks after transplanting. Pod
weight per plot and marketable yield per plot were measured
at 7 weeks after transplanting. Analysis of variance of
data was calculated using SAS 8.12 (SAS Institute, N.C).
A correlation test was used to !nd out the best soil P
extracting reagent for yard long bean in acid soil (Ultisols).
Determination of soil P-response categories was conducted
based on the best crop response to soil P-extracting reagents.
The soil P response was divided into four categories; very
low if relative yield (RY) < 50%, low RY 50-75%, medium
RY 75-100%, and high RY = 100%. The critical border
to determine P soil index for each group is shown in the
calibration curve correlating P soil index (X) and relative
yield (Y). An orthogonal polynomial test was used to !nd
out the optimum fertilizer rate of P for maximum yield for
each soil response category.
Anas Dinurrohman Susila, Juang Gema Kartika, Tisna Prasetyo, and Manuel Celiz Palada
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
RESULTS AND DISCUSSION
Plant Growth and Yield
The effect of soil P status on plant height and stem
diameter was not signi!cant except on plant height at 2
weeks after planting. Application of P fertilizer to build
up soil P status from 0 to X = 1,590.5 kg SP-36 ha-1 (36%
P2O5) increased linearly for plant height from 2 weeks after
planting (Table 1). The same response was obtained on
marketable yield per plot (Table 2). Soil P status from 0
to 1,591 g SP-36 ha-1 increased marketable yield per plot
linearly from 2,167.4 to 2,920.6 g plot-1. However, there
was no signi!cant effect on non-marketable yield per plot
and pod length. These results indicated that the range of
soil P status in the research site was wide enough to build
a correlation study between soil P status and yield response
of yard long bean.
Correlation between Soil Extracted-P and Yield
Five different soil-P extraction methods resulted in
different soil-P indices. The strongest extracting reagents to
the weakest were HCl 25% (521–1,565 ppm P2O5) followed
by Mechlich-1 (30–841 ppm P2O5), Truog (13-489 ppm
P2O5), Olsen (43–417 ppm P2O5), Bray-1 (23-414 ppm
P2O5), Morgan Vanema (1–18 ppm P2O5), and water (0.1–1.6
ppm P2O5). Extracted-P by different extraction methods on
different P-application rates on Ultisols is presented in Table
3. The strongest extraction methods was not necessarily be
the best solution for soil P extraction. The ideal soil test
has the following characteristics: 1) the extracting reagent
is effective for most, if not all plant mineral nutrients, and
for all soil types, 2) the procedure accurately measures the
plant-availability of the nutrient, and 3) the test is simple,
inexpensive, quick, reproducible, and sensitive to all soil
factors controlling nutrient availability (Skogley, 1994).
In order for a soil test to be useful, there must be a
positive correlation between the index and the crop response
(yield). The best extraction method will mimic how the
plant root extracts P from the soil, therefore it will have
good correlation with plant yield. The highest coef!cient
correlation to the lowest was Olsen (0.772), Bray-1 (0.765),
HCl 25% (0.755), Mechlich-1 (0.732), Morgan Vanema
(0.650), Water (0.623), and Truog (0.266) (Table 4). For an
extracting reagent to be effective, it requires that a low index
Table 1. The effect of soil P status on plant height and stem diameter of yard long bean at 2, 3, and 4 weeks after planting
Soil P status by application
of SP-36 (kg ha-1)
0
(0X)
398 (1/4X)
795 (1/2X)
1193 (3/4X)
1591 (X)
Response
2
17.54b
18.88a
18.58a
19.28a
19.53a
L**
Plant height
(weeks after planting)
3
cm
42.67
51.54
48.64
49.01
53.47
NS
4
2
123.68
140.57
135.13
135.91
139.88
NS
0.317
0.364
0.387
0.349
0.411
NS
Stem diameter
(weeks after planting)
3
cm
0.413
0.440
0.449
0.459
0.467
NS
4
0.485
0.498
0.505
0.534
0.524
NS
Note: * = Signi!cant at 5% F test; ** = signi!cant on 1% F test; NS = Not Signi!cant; L = Linear
Table 2. The effect of soil P status on marketable yield, non-marketable yield and pod length of yard long bean
Soil P status by application of SP-36
(kg ha-1)
Marketable yield per plot
0
(0X)
398 (1/4X)
795 (1/2X)
1193 (3/4X)
1591 (X)
Response
g
2167.4 b
2614.2 ab
2816.4 ab
3058.0 a
2920.6 ab
L*
Non-marketable yield
per plot
g
372.68
474.40
435.18
515.61
485.91
NS
Pod length
cm
56.09
57.75
58.33
57.73
58.82
NS
Note: * = Signi!cant on 5% F test; NS = Not Signi!cant; L = Linear
Fertilizer Recommendation: Correlation and Calibration......
227
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
be related to reduced growth responses for a crop grown on
that soil, and conversely, a high index be related to maximum
crops response (Dahnke and Olson, 1990). Soil-P extraction
methods with coef!cient correlation > 0.7 (Olsen, Bray-1,
HCL 25%, Mechlich-1) can be recommended to test soil P
for yard long bean in Ultisols Nanggung, Bogor. However,
evaluation of the operational cost and reproducibility of that
extraction reagent is still needed.
Calibration of the Soil P Test
Once a good correlation between indices produced by
the extracting reagent and crop response is established, soil
test indices are usually grouped into response categories so
that the indices can be interpreted and become meaningful.
By plotting of percent relative yields and corresponding
extracted-P, it can be determined plant response categories
of that soil. Yard long bean relative yield plotted against
extracted-P by Olsen reagent is presented in Figure 1.
Extracted-P concentration # 18.40 ppm resulted in # 50%
crop relative yield and therefore was termed “very low”. A
“low” response category result of 50% to 75% of relative
yield was obtained where soil extracted-P was > 18.40 to <
117.27 ppm. A “medium” response category result of 75%
to 100% of relative yield was obtained where soil extractedP was > 117.27 to < 267.04 ppm, while a “high” response
category result of $ 100% of relative yield was obtained for
soil extracted-P $ 267.04 ppm.
Table 3. Extracted-P by various extraction methods from different P fertilizer rates on Ultisols, Nanggung, Bogor
Soil P status by
application of
SP-36 (kg ha-1)
0 (0X)
397,625 (1/4X)
795,250 (1/2X)
1,192,875 (3/4X)
Truog
54 ± 35.55
58 ± 54.22
77 ± 61.29
314 ± 151.84
Mechlich-1
HCl 25%
Olsen
Bray 1
(P2O5 ppm)
Water
Morgan
Vanema
------------------------- Extracted-P ----------------------51 ± 27.59
613 ± 114.18
62 ± 17.35
34 ± 1290
0.2 ± 0.10
2 ± 0.00
94 ± 29.57
704 ± 129.00 118 ± 100
60 ± 16.65 0.13 ± 0.06 2.3 ± 1.53
182 ± 91.76
742 ± 165.77 126 ± 43.41 108 ± 60.78 0.33 ± 0.23 5.3 ± 3.06
487 ± 309.02 1317 ± 303.04 324 ± 95.04 263 ± 132.22 0.37 ± 0.15 10.7 ± 6.66
Table 4. Correlation between extracted-P by different extraction reagents with yard long bean relative yield on Ultisols,
Nanggung, Bogor
Extraction reagent
Truog
Mechlich-1
HCl 25%
Olsen
Bray-1
Water
Morgan Vanema
Linear equation
RY= 70.563 + 0.064 P
RY= 66.673 + 0.052 P
RY= 47.280 + 0.034 P
RY= 61.548 + 0.097 P
RY= 64.248 + 0.108 P
RY= 67.724 + 32.239 P
RY= 66.465 + 2.239 P
Figure 1. Plot of relative yield and corresponding extracted-P using
Olsen extraction method in Ultisols, Nanggung, Bogor.
VL = Very Low, L = Low, M = Medium, H = High
228
Coef!cient correlation
0.566
0.732
0.755
0.772
0.765
0.623
0.650
Figure 2. Plot of relative yield and corresponding extracted-P using
Bray-1 extraction method in Ultisols, Nanggung, Bogor.
VL = Very Low, L = Low, M = Medium, H = High
Anas Dinurrohman Susila, Juang Gema Kartika, Tisna Prasetyo, and Manuel Celiz Palada
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
Plots of extracted-P by Bray-1 reagent with yard long
bean relative yield can be seen in Figure 2. There was no
“very low” response category obtained by Bray-1 soil P test
from this study. A “low” response category result (# 75%
of relative yield) was obtained with soil extracted-P # 87.81
ppm, a “medium” response category result (75 % to 100 %
relative yield) was obtained with soil extracted-P between
< 87.81 to < 233.78 ppm, while a “high” response category
result of $ 100% of relative yield was obtained with soil
extracted-P $ 233.78 ppm. The Olsen and Bray-1 soil test
calibration for yard long bean in Ultisols, Nanggung, Bogor
can be seen in Table 5.
Fertilizer Recommendation
The objectives of grouping soil test indices into
responses categories are to recommend the quantity of
fertilizer required for those sites to produce maximum yield.
The relationship between P-fertilizer rate and relative yield
of yard long bean on Ultisols, Nanggung, Bogor, based
on response category determined by different extraction
methods, can be seen in Figure 3. Based on Olsen extraction
methods, under “low” soil response category the regression
equation was RY = -0.00065x2 + 0.24147x + 62.89249, R2
= 0.26677. From this regression model, optimum predicted
P-fertilizer rate was 185.75 kg P2O5 ha-1 or equal to 515.96
kg SP-36 ha-1 (36% P2O5). Under “medium” soil response
category the regression equation was RY = -0.00068x2 +
0.23796x + 52.22694, R2 = 0.41078. Optimum predicted Pfertilizer rate for “medium” soil P response category was
174.97 kg P2O5 ha-1 or equal to 486.03 kg SP-36 ha-1 (36%
P2O5). Predicted P-fertilizer recommendation rate based on
soil-P response category can be seen in Table 6.
Based on Bray-1 extraction method, under “low”
soil response category the regression equation was RY =
-0.00059x2 + 0.21749x + 63.92204, R2 = 0.23603. From
this regression model, optimum predicted P-fertilizer rate
was 184.31 kg P2O5 ha-1 or equal to 511.98 kg SP-36 ha-1
(36% P2O5). Under “medium” soil response category the
regression equation was RY = -0.00099x2 + 0.31956x +
53.69884, R2 = 0.50473. Optimum predicted P-fertilizer
rate for “medium” soil P response category was 161.39 kg
P2O5 ha-1 or equal to 448.32 kg SP-36 ha-1 (36% P2O5).
Although there were differences in soil P category values
between Olsen and Bray-1 extraction methods, the predicted
P fertilizer recommendation were similar for the same soil P
category responses.
Figure 3. Relationship between P-fertilizer rate and relative yield of yard long bean on Ultisols, Nanggung, Bogor based on response
category determined by different extraction methods (A) Low soil-P response category by Olsen (B) Medium soil-P response
category by Olsen (C) Low soil-P response category by Bray-1 (D) Medium soil-P response category by Bray-1
Fertilizer Recommendation: Correlation and Calibration......
229
J. Agron. Indonesia 38 (3) : 225 - 231 (2010)
Table 5. The Olsen and Bray-1 soil test calibration for yard long bean in Ultisols, Nanggung, Bogor
Response category
Extracted-P (ppm P2O5)
Relative yield (%)
Very low
Low
Medium
High
Olsen
# 18.40
> 18.40 - < 117.27
> 117.27 - < 267.04
$ 267.04
# 50
> 50 - < 75
> 75 - < 100
$ 100
Bray I
# 87.81
< 87.81 - < 233.78
$ 233.78
Table 6. Predicted P-fertilizer recommendation rate for yard long bean in Ultisols, Nanggung , Bogor, based on soil-P
response category
Soil-P response
category
Olsen
Low
Medium
Bray-1
Low
Medium
Predicted P-rate (kg ha-1)
P2O5
SP-36
R2
185.75
174.97
515.96
486.03
RY = -0.00065x2 + 0.24147x + 62.892
RY = -0.00068x2 + 0.23796x + 52.227
0.26677
0.41078
184.31
161.39
511.98
448.32
RY = -0.00059x2 + 0.21749x + 63.922
RY = -0.00099x2 + 0.31956x + 53.699
0.23603
0.50473
CONCLUSION
From this study it can be concluded that Olsen, Bray-1,
HCl 25%, and Mechlich-1 soil test can be used to determine
soil-P for yard long bean production in Ultisols-Nanggung.
The coef!cient correlation (r) of extraction reagent Olsen,
Bray-1, HCl 25%, and Mechlich-1 were 0.772, 0.765, 0.755,
and 0.732, respectively. With the Olsen soil test, UltisolsNanggung can be divided into very low, low, medium and
high soil response category. However with the Bray-1 soil
test they only can be divided into low, medium, and high
soil response categories.
ACKNOWLEDGEMENT
This publication was made possible through support
provided by the United States Agency for International
Development and the generous support of the American
People (USAID) for the Sustainable Agriculture and Natural
Resources Management Collaborative Research Support
Program (SANREM CRSP) under terms of Cooperative
Agreement Award No. EPP-A-00-04-00013-00 to the Of!ce
of International Research and Development (OIRED) at
Virginia Polytechnic Institute and State University (Virginia
Tech).
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